1) Field of the Invention
The invention is in the field of Microelectromechanical Systems (MEMS).
2) Description of Related Art
For the past several years, MEMS structures have been playing an increasingly important role in consumer products. For example, MEMS devices, such as sensors, detectors and mirrors, can be found in products ranging from air-bag triggers in vehicles to displays in the visual arts industry. As these technologies mature, the demands on precision and functionality of the MEMS structures have escalated. For example, optimal performance may depend on the ability to fine-tune the characteristics of various components of these MEMS structures. Furthermore, consistency requirements for the performance of MEMS devices (both intra-device and device-to-device) often dictates that the processes used to fabricate such MEMS devices need to be extremely sophisticated.
A recent fabrication challenge in the field MEMS devices is the integration of MEMS structures with complimentary metal-oxide-silicon (CMOS) architectures. These devices hold the promise of reducing cost and power requirements in integrated circuits (ICs) for a variety of applications. However, several issues arise as a result of integrating MEMS technology with semiconductor IC technologies. For example, once fabricated, semiconductor ICs may have a temperature threshold above which the IC irreversibly degrades. Thus, it may be difficult to subsequently fabricate a MEMS device incorporated with a semiconductor IC structure. One approach has been to form the semiconductor IC on an already fabricated MEMS structure. This process has its limitations, however, since many semiconductor ICs require the use of virgin substrates for optimal performance.
Another approach has been to fabricate a MEMS device in the back end-of-line (BEOL) processing of a semiconductor IC, incorporating the MEMS structure into a plurality of interconnects. For example, FIG. 1 illustrates a cross-sectional view representing a MEMS resonator integrated with a plurality of interconnects, in accordance with the prior art. A MEMS resonator 102 having a resonating member 104 is connected to a plurality of interconnects 106 in a BEOL portion 100 of a semiconductor IC. A single port electrode in one level of the plurality of interconnects 106 drives and senses the resonating member 104 from a different level of the plurality of interconnects 106. Drawbacks to this approach stem from the requirement that the resonating member and the driver/sensor electrode are in different levels of the plurality of interconnects. This arrangement may be optimized to have only a one-port configuration, and thus undesirably demonstrate increased parasitics, and may exhibit fabrication limitations since each component is in a different level of the interconnects.
Thus, an IC-compatible MEMS structure is described herein, along with a method to fabricate such a MEMS structure.